Colored preprinting of electrostatic copy paper

ABSTRACT

Colored inks having a color other than that of a toner are provided for the preprinting of electrostatic copy paper in which the differing color of the preprint remains even after the electrostatic copy paper is conventionally electrostatically imaged and fixed with toner. The present colored inks and resulting preprint image areas on an electrostatic copy paper comprise principally a colorant, preferably a substantially translucent dye, and an electroconductive polymer comprising a polymerized vinylbenzene quaternary ammonium compound, such as vinylbenzyl trimethyl ammonium chloride. Upon being radiated, a preprint area of a present electrostatic copy paper does not interfere with the discharge of a corresponding, underlying area of the copy paper so that, in effect, the charging and photodischarging of the copy paper ignore the presence of the preprint area.

Romig Jan. 7, 1975 COLORED PREPRINTING OF ELECTROSTATIC COPY PAPER John R. Romig, Euclid, Ohio Addressograph-Multigraph Corporation, Cleveland, Ohio Filed: June 29, 1973 Appl. No.: 375,258

Related US. Application Data Continuation of Ser. No. 175,689, Aug. 27, 1971, abandoned.

Inventor:

Assignee:

US. Cl 96/1.2, 96/1.6, 117/35.6 Int. Cl 603g 5/04 Field of Search 96/1.2, 1.3, 1.4, 1.6;

References Cited UNlTED STATES PATENTS Primary ExaminerNorman G. Torchin Assistant Examiner.l0hn L. Goodrow Attorney, Agent, or Firm-Sol L. Goldstein; Michael Kondzella; Russell L. Root [57] ABSTRACT Colored inks having a color other than that of a toner are provided for the preprinting of electrostatic copy paper in which the differing color of the preprint remains even after the electrostatic copy paper is conventionally electrostatically imaged and fixed with toner. The present colored inks and resulting preprint image areas on an electrostatic copy paper comprise principally a colorant, preferably a substantially translucent dye, and an electroconductive polymer comprising a polymerized vinylbenzene quaternary ammo nium compound, such as vinylbenzyl trimethyl ammonium chloride. Upon being radiated, a preprint area of a present electrostatic copy paper does not interfere with the discharge of a corresponding, underlying area of the copy paper so that, in effect, the charging and photodischarging of the copy paper ignore the presence of the preprint area.

7 Claims, 2 Drawing Figures COLORED PREPRINTING F ELECTROSTATIC COPY PAPER This is a continuation of application Ser. No. 175,689 filed Aug. 27, 1971, now abandoned.

BACKGROUND OF THE INVENTION Electrostatic printing, which is taken to include electrophotography and xerography, has become increasingly popular. In a typical process, electrostatic copy paper is used comprising a base or backing member having a photoconductive coating, usually of zinc oxide dispersed in an insulating binder. An electrical charge is placed over the entire face of the copy paper which is then imaged by directing light or other radiant energy on selected areas of the copy paper in accordance with a desired pattern. The areas of the copy paper so radiated are electrostatically discharged, while the remaining, non-radiated areas retain their charge to define an electrostatic image. A developer, normally termed a toner, is next applied and attracted to the charged electrostatic image areas. The toner can be either a dry powder or a powder suspended in an insulating liquid dispersent. The powder image so formed may be fixed directly to the photoconductive material, or it may be transferred to still another surface upon which the reproduced image may then be fixed. In either case, fixing the powder or toner commonly comprises fusing the developer powder to a surface, such as that of the photoconductive material on the copy paper, by the application of heat.

The use of preprinted indicia on forms, such as letterheads, order forms, bulletins, and the like, is common in industry. Often it is desirable to preprint with colored inks for style and attractiveness, or for code identification such as in collated forms, or for still other reasons. To applicants knowledge, it has not been possible previously to preprint electrostatic copy paper with inks having a color different from that of the toner which is usually black. Conventional lithographic inks either form preprint areas which electrostatically insulate corresponding areas of the underlying photoconductive coating of the copy paper, so that the charge of such underlying areas is not readily dispersed; or an electrostatic charge remains on the surface of the dried preprint ink itself. When such a copy paper is subsequently electrostatically imaged and fixed with toner, the preprint areas act as though they are part of the desired electrostatic image and attract toner, thereby converting its color to that of the toner. Accordingly, it was not previously possible to preserve the color of a preprint on electrostatic copy paper which contrasted in color with that of the toner.

SUMMARY OF THE INVENTION In accordance with the present invention, nonelectrostatically-reproducing inks, that is, inks which do not attract toner, form preprint areas on electrostatic copy paper. The inks may have various attractive colors, differing from that of the toner, the colors of the inks being preserved when a preprinted electrostatic copy paper is later conventionally eleetrostatically imaged and fixed with toner.

These results are due principally to the use of an electroconductive polymer in the preprint image areas which enables the electrostatic imaging step of an elec trostatic printing process effectively to ignore the presence of the preprint. As a result, all areas of a photoconductive coating of the electrostatic copy paper desired to be discharged are, in fact, discharged, and the colored preprint areas do not later attract toner. The electroconductive polymer comprises polymerized vinylbenzyl quaternary ammonium compounds, for example, vinylbenzyl trimethyl ammonium chloride.

In use, a colorant is added to the polymer merely to impart a contrasting color and make a preprinted image readily discernible. Preferably, the colorant is a translucent dye to facilitate transmission of light or other energy radiated onto the copy paper during an electrostatic process. A suitable fugitive dispersant or solvent, such as ethylene glycol, is added to the polymet to form an ink and provide carrier means by which the polymer and colorant are readily applied to electrostatic copy paper. The dispersant or solvent thereafter leaves the copy paper as by evaporation. The ink may be applied to copy paper by any convenient means such as by relief printing.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 is a schematic plan view of a sheet of conventional electrostatic copy paper having a preprint image of the present invention; and

FIG. 2 is a fragmentary, greatly enlarged section of FIG. 1 on the line 22 and diagrammatically illustrates the component parts of the preprinted electrostatic copy paper, the relative sizes of the layers being magni fied for purposes of illustration and otherwise having ,no significance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to the inks of the present invention, the basic components comprise an electroconductive polymer, a colorant, and a liquid fugitive medium or vehicle which serves merely to transfer the polymer and colorant to electrostatic copy paper.

The class of electroconductive polymers useful in the present invention is described in Us Pat. 3,011,918 to Silvernail et al. which is hereby incorporated by reference. These polymers comprise any water-soluble or water-dispersible homopolymer or copolymer of one or more vinylbenzyl quaternary ammonium compounds, or copolymers of a predominant amount of a vinylbenzyl quaternary ammonium compound and a minor amount of a nonacidic copolymerizable compound such as acrylamide, or copolymers containing in the polymer molecules residues corresponding to from 95.0 to 99.99 per cent by weight of one or more vinylbenzyl quaternary ammonium compounds and from 5.0 to 0.01 per cent by weight of divinylbenzene.

In particular, the electroconductive polymers can be a homopolymer or a copolymer of any two or more vinylbenzyl quaternary ammonium compounds having the general formulai wherein R, R and R" each represents individually a monovalent radical selected from the group consisting of CH Ol-ICI-I CI-l CI-IOHCH CH Ol-ICI-IOHO H and alkyl, aryl, cycloalkyl and aralkyl hydrocarbon radicals, and R, R and R collectively represent the trivalent radical of the formula:

CH-CH:

wherein the three valences are attached to the nitrogen atom, such R groups containing a total of not more than 12 carbon atoms in the sum of the constituent radicals; or a copolymer of at least 65 per cent by weight of any one or more of such vinylbenzyl quaternary ammonium compounds with not more than 35 per cent by weight of acrylamide; or a copolymer containing in the polymer molecules residues corresponding to from 95.0 to 99.99, preferably from 99.0 to 99.99, per cent by weight of any one or more of such vinylbenzyl quaternary ammonium compounds and from 5.0 to 0.01, preferably from 1.0 to 0.01 per cent by weight of divinylbenzene. Mixtures of any two or more of the homopolymers or copolymers can also be used.

The polymers are of relatively high molecular weight and are characterized by a viscosity of at least 2 centipoises for a 0.5 per cent by weight solution of the polymer in an aqueous 2 per cent by weight solution of sodium chloride at 25C. as determined with an Ostwald viscosimeter. The term viscosity as herein employed refers to the viscosity of the described polymer solutions or dispersions under the above conditions.

In a preferred embodiment of the electroconductive polymer, the polymer is a homopolymer or copolymer of one or more vinylbenzyl quaternary ammonium compounds having the previously described general formula wherein R represents an alkyl radical containing from 1 to 4 carbon atoms, R and R" each represents a radical of the group consisting of CH OHCH CH CHOHCH CH OHCHOHCl-l and lower alkyl radicals containing from 1 to 4 carbon atoms, and Y is an anion, for example, a sulfate, a chloride, a nitrate, or a hydroxyl ion; copolymers of at least 65 per cent by weight of any two or more of such vinylbenzyl quaternary ammonium compounds and not more than 35 per cent by weight of acrylamide; or copolymers of from 99.0 to 99.99 per cent by weight of at least one such vinylbenzyl quaternary ammonium compound and from 1.0 to 0.01 per cent by weight of divinylbenzene.

The preparation of the polymerized vinylbenzene quaternary ammonium compounds is also described in the cited US. Pat. No. 3,011,918 to Silvernail et a]. In general, as an example, vinylbenzene chloride or bromide is reacted with a tertiary amine such as trimethylamine. The reaction of the vinylbenzyl halide and the tertiary amine proceeds readily at temperatures between about C. and 60C. The reaction can be carried out in admixture with, or in the presence of, a solvent or reaction medium such as water, ethyl alcohol, ethylene dichloride, toluene, or the like. A solvent is not, however, required. The vinylbenzyl quaternary ammonium compounds can be polymerized either alone or in admixture with each other, or in admixture with acrylamide or divinylbenzene in the proportions previously stated, to form the polymers for use as described in the present invention.

The role of the colorant is merely to make a preprint area discernible to the eye. The colorant differs in color from that of the toner or developer, which is usually black, to provide an attractive, eye-catching appearance. As long as the colorant does not interfere with the transfer of light or other radiant energy through the preprint image to discharge underlying areas of a pho toconductive coating, the colorant may be any of those materials known in the art for this purpose, whether applied as dispersed solid particles as in the case of pigments or as a dissolved solute as in the case of dyes. However, a preferred class of colorants comprises dyes and particularly translucent dyes which interfere the least with the passing of light through a preprint image. Those dyes known in the art as spirit-soluble dyes have been found to be best. Such dyes are soluble in alcohols, including glycols, and are soluble in water although to a lesser extent. In general, any of the multitudinous alcohol-soluble and water-soluble dyes may be used as the colorant. A desirable class of dyes are those sold by the American Cyanamid Company under'the trademark CALCOClD. These are acid dyes comprised of colored organic chemicals from the nitro, azo, pyrazolone, quinoline, triphenylmethane, diphenylnaphthylmethane, azine, xanthene, and anthraquinone groups. Most of these dyes are manufactured as mono, di or tri sodium sulfonate derivatives of soluble color acids. As a group they offer a full range of fairly bright hues of good tinctorial power.

In accordance with the basic concept of the invention, it is necessary only to apply the electroconductive polymer and colorant in admixture to a photoconductive coating of electrostatic copy paper. This may be accomplished by any conventional means. The fugitive liquid medium or vehicle can be any liquid dispersant or solvent for the polymer and colorant which is normally nonreactive with these materials. However, when it is preferred to apply the preprinting ink for long runs by standard printing means such as relief printing, the ink should have the following properties:

1. Volatility Inert components of the ink should not be too volatile or the ink will dry on the printing rolls and plate, yet the components should be volatile enough to permit the ink to dry on the copy paper within a reasonable time.

2. Solvency The slightly volatile liquid vehicle preferably has a solvating effect on colorants and the electroconductive polymer without unduly penetrating or attacking the rubber printing rolls or printing plate.

3. Surface Tension The inks should have a surface tension lower than that of water to provide good spreading on the rolls and printing plate but not on copy paper.

4. Viscosity The viscosity should be sufficiently high to give a good printing film but low enough to permit some penetration of the ink into the copy paper surface to aid drying.

5. Transparency The dried ink film should be sufficiently transparent to the copier exposure light to permit the discharge of the photoconductive surface under the ink film.

6. Conductivity The dried ink film should be sufficiently conductive to prevent retention of a static charge on its surface.

7. Toxicity The ingredientsof the ink should meet minimum industrial toxicity standards.

Present inks having low molecular weight glycols as the fugitive liquid vehicle meet these requirements, since glycols provide a good balance of such requirements as volatility, solvency, viscosity, and surface ten sion. Such glycols include propylene glycol, butylene glycol, and preferably ethylene glycol. Properties designated No. 5 and No. 6 should be present in a preprint area of the present invention, no matter what the physical characteristics might be of the admixture from which the electroconductive polymer and colorant are applied.

Amounts present in the inks are not critical. A sufficient amount of the colorant should be present to make the preprinted image discernible and may be present up to a maximum which blocks light or other radiant energy, such that the underlying areas of a photoconductive layer are not discharged during the electrostatic printing process. Such maximum is easily determined by trial and error. Similarly, enough of the electroconductive polymer should be present to make a dried ink film sufficiently conductive to prevent retention of a static charge on its surface. There is no practical upper limit of the amount of the electroconductive polymer which may be used, as long as it does not interfere with the function of the colorant.

In general, the present inks may comprise in weight from about 0.5 per cent to about 6 per cent of the colorant, from about 45 per cent to about 95 per cent of the fugitive vehicle, and from about 2 per cent to about 50 per cent of an aqueous solution or dispersion containing about 33.5 per cent of the electroconductive polymer. The dried preprint image may, as an example, comprise from about per cent to about 98 per cent by weight of the electroconductive polymer, the balance comprising principally the colorant. Another advantage of the present electroconductive polymers in the present environment is that they retain water, obtained either from the liquid vehicle or elsewhere, in fairly appreciable amounts, for example, from about 5 per cent to about 10 per cent or more by weight. The retained water in this environment of use contributes to the desired electroconductivity.

FIGS. 1 and 2 diagrammatically illustrate an electrostatic copy paper of the present invention and its manner of use. A sheet of conventional copy paper, generally indicated at 5, includes a layer of coated paper 6 which may comprise a smooth, uniform, non-porous paper of base weight in the range of 30 to 45 pounds per 3,000 square feet (one ream) impregnated and coated, for example, with starch modified with pigments, latexes, and the like. A photoconductive coating 7 is applied by known coating techniques to one side of the precoated paper 6 and, if desired, to the other side as well. The photoconductive coating 7 comprises zinc oxide dispersed in an insulating binder. In place of zinc oxide, other photoconductive materials known in the art may be used such as selenium. Copy sheet 5 has a red preprinted image 8 applied in accordance with the present invention and defining communicating indicia.

When copy sheet 5 is conventionally electrostatically charged and then radiated with light or other radiant energy to provide an electrostatic image, the light represented by arrows 9 in HO. 2 treats the photoconductive coating 7 uniformly, that is, the light simply ignores the presence of the printed indicia 8. insofar as an electrostatic copy process is concerned, the colored printing image 8 does not exist. Accordingly, when toner is subsequently applied, it is not attracted to the preprinted image 8 which retains its color unchanged, because the areas of the coating 7 directly beneath pre- EXAMPLE 1 An ink was prepared having this composition:

Spirit Red Dye Ethylene Glycol Dow ECR 34 The spirit-soluble red dye was purchased under the trademark Cyanamid Calcofast 2 G Spirit Red. Dow ECR 34 is a proprietary mixture having this composition and properties:

Parts (Solids Basis) Finely divided clay 50 Polymeric vinylhcnzyl trimethyl ammonium chloride Starch The starch and clay are fillers and binders and are not essential to the use of the electroconductive polymer. Sufficient water was added to provide 25 per cent solids and a Brookfield Viscosity of 240 at 20 rpm and 74F.

The ink was applied by relief printing to a series of conventional electrostatic copy paper to form a preprint image on each sheet. Some of the preprinted electrostatic copy paper was subsequently exposed in a known electrostatic printing process, such as the Electrofax Process, and toner subsequently applied. None of the toner remained on the preprint image which retained its red color.

EXAMPLE 2 A procedure was carried out like the procedure of Example lexcept that the ink had this composition:

Spirit Blue Dye Ethylene Glycol Dow ECR 34 EXAMPLE 3 A procedure was carried out like the procedure of Example 1 except that the ink had this composition:

Spirit Blue Dye Spirit Yellow Dye Ethylene Glycol Dow ECR 34 The spirit-soluble blue dye was the same used in Example 2, namely, Calcocid Blue 2 G. The spirit-soluble yellow dye was purchased under the trademark Calcocid Fast Yellow 3 G.

When the resulting preprinted copy sheets were electrostatically imaged and developed, none of the toner remained in the preprinted image which retained a green color.

EXAMPLE 4 A procedure was carried out like the procedure of Example 1, except that the ink had this composition:

Spirit Yellow Dye 4.3% Ethylene Glycol 5 l.8% Dow ECR 34 43.0% Non-ionic Surfactant 0.9%

The spirit-soluble yellow dye was purchased under the trademark Calcocid Fast Yellow 3 G. The surfactant was used to lower the surface tension and could be any of those known in the art for this purpose, such as Tergitol Non-ionic NPX.

When the resulting preprinted color sheets were electrostatically imaged and developed, none of the toner remained on the preprint image which retained its yellow color.

While the foregoing describes several embodiments of the present invention, it is understood that the invention may be practiced in still other forms within the scope of the following claims.

I claim:

1. A process for preparing copies of an original from electrostatic copy paper and the like having a photoconductive coating adapted to be electrostatically imaged and developed by toner having a first color without affecting a preprinted image in a second color thereon, comprising forming on said photoconductive coating a preprinted image, said image being formed of a composition which is transparent to the transmission of energy capable of charging and discharging said underlying photoconductive coating comprising a colorant having a second color, and an electroconductive polymer consisting essentially of at least one member of the group consisting of (a) homopolymers of a vinylbenzyl quaternary ammonium compound having the general formula:

R H O=CHC H CH2-N-R Y RI! wherein R, R, and R" each represents individually a monovalent radical selected from the group consisting of and alkyl, aryl, cycloalkyl and aralkyl hydrocarbon radicals, and R, R and R" collectively represent the trivalent radical of the formula:

(in n wherein the three valences are attached to the nitrogen atom and Y is an anion, said R groups containing a total of not more than 12 carbon atoms in the substituent radicals, (b) copolymers of at least two of such vinylbenzyl quaternary ammonium compounds, (c) copolymers of at least 65% by weight of at least one of such vinylbenzyl quaternary ammonium compounds and not more than 35% by weight of acrylamide, and (d) copolymers corresponding to from 95.0% to 99.99% by weight of at least one of such vinylbenzyl quaternary ammonium compounds and from 5.0% to 0.01% by weight of divinylbenzene, a sufficient amount of said elecroconductive polymer being present to render said preprinted image electroconducting,

electrostatically charging said photoconductive coatimaging the chargedphotoconductive coating, by exposing to actinic radiation in a pattern corresponding to said original to discharge selected radiated areas including at least some areas thereof underlying said preprinted image,

and applying and fixing toner of said first color over non-discharged areas of said photoconductive coating.

2. A process according to claim 1 wherein the entire area underlying said preprinted image is discharged.

3. A process according to claim 1 in which said electroconductive polymer is a homopolymer of vinylbenzyl trimethyl ammonium chloride.

4. A process according to claim 1 wherein said electroconductive polymer is a copolymer of vinylbenzyl trimethyl ammonium chloride and acrylamide.

5. A process according to claim 1 in which said electroconductive polymer is a copolymer of vinylbenzyl trimethyl ammonium chloride and divinylbenzene.

6. A process according to claim 1 in which said preprinted image contains from about 10% by weight of said electroconductive polymer.

7. A process according to claim 1 in which said colorant is a translucent dye.

UNITED STATES- PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,859,088 Dated January 7, 1975 Inventofl) John R. Romig It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 41, change "s" to S (in U.S.)

Column 6, line 6, after "case," insert as desired,

Column 8, line 25, change "elecroconductive" to electroconductive Claim 6,. after "10%" insert to about 98% Signed and sealed this 8th day of April 1975.

(SEAL) Attest:

G. M9 "\SPALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks FORM po'wso (wss) I uscoMM-oc 60376-P69 0.5. GOVERNMENT PRINTING OFFICE 2 '9" "6-33 

1. A PROCESS FOR PREPARING COPIES OF AN ORIGINAL FROM ELECTROSTATIC COPY PAPER AND THE LIKE HAVING A PHOTOCONDUCTIVE COATING ADAPTED TO BE ELECTROSTATICALLY IMAGED AND DEVELOPED BY TONER HAVING A FIRST COLOR WITHOUT AFFECTING A PREPRINTED IMAGE IN A SECOND COLOR THEREON, COMPRISING FORMING ON SAID PHOTOCONDUCTIVE COATING A PREPRINTED IMAGE, SAID IMAGE BEING FORMED OF A COMPOSITION WHICH IS TRANSPARENT TO THE TRANSMISSION OF ENERGY CAPABLE OF CHARGING AND DISCHARGEING SAID UNDERLYING PHOTOCONDUCTIVE COATING COMPRISING A COLORANT HAVING A SECOND COLOR, AND AN ELECTROCONDUCTIVE POLYMER CONSISTING ESSENTIALLY OF AT LEAST ONE MEMBER OF THE GROUP CONSISTING (A) HOMOPOLYMERS OF A VINYLBENZYL QUATERNARY AMMONIUM COMPOUND HAVING THE GENERAL FORMULA:
 2. A process according to claim 1 wherein the entire area underlying said preprinted image is discharged.
 3. A process according to claim 1 in which said electroconductive polymer is a homopolymer of vinylbenzyl trimethyl ammonium chloride.
 4. A process according to claim 1 wherein said electroconductive polymer is a copolymer of vinylbenzyl trimethyl ammonium chloride and acrylamide.
 5. A process according to claim 1 in which said electroconductive polymer is a copolymer of vinylbenzyl trimethyl ammonium chloride and divinylbenzene.
 6. A process according to claim 1 in which said preprinted image contains from about 10% by weight of said electroconductive polymer.
 7. A process according to claim 1 in which said colorant is a translucent dye. 